TAMOXIFEN MIMICS THE EFFECTS OF ESTRADIOL ON FOOD-INTAKE, BODY-WEIGHT, AND BODY-COMPOSITION IN RATS

Treatment of ovariectomized rats with the nonsteroidal antiestrogen ta moxifen mimicked the effects of estradiol and caused significant decre ases in food intake and body weight. The decreases in body weight were reflected mainly in a decreased body fat content, although tamoxifen treatment did suppress linear growth too. Similar to the effects of es tradiol, tamoxifen decreased parametrial white adipose tissue wet weig ht and lipoprotein lipase activity. When given concurrently with estra diol, tamoxifen showed no evidence of antiestrogenic activity on any o f these measures. As reported previously, tamoxifen acted as a partial agonist/antagonist for uterine weight. The effective dose of tamoxife n for suppression of food intake, body weight, and body fat content fe ll between 10 and 50 mug/day. Therefore, tamoxifen behaves like other nonsteroidal antiestrogens and mimics but fails to antagonize the acti ons of estradiol on many aspects of physiological and behavioral regul ation of energy balance.